Fishing is a sport which is under constant scrutiny from animal welfare groups. Anglers argue that in competition fishing, the fish is caught, weighed and subsequently released causing no harm to the fish.
Many devices are commercially available for weighing fish. One such device is a simple set of weighing scales where the live fish is placed into a weighing pan and the weight is read from a display. The problem with this type of arrangement for weighing live fish is they may fall out of the pan whilst struggling to escape, causing injury or even death. The fish is also kept out of water for a prolonged period of time depriving it of oxygen.
Another device for weighing fish includes a hook on the end of a spring weighing scale. An operator pierces the fish's lip with the hook and the device is lifted vertically to take a reading. A variation of this device uses a clamp to hold the fish's bottom lip. Clearly these two methods exhibit an increased level of interference with the fish and consequential stress and risk.
Two US patents (U.S. Pat. No. 4,631,851 Whitehurst and U.S. Pat. No. 4,765,420 Mengo) have been identified which incorporate mechanical spring scales and a net into one device, the advantage of this arrangement being that the fish do not need to be removed from the net for weighing.
Both US patents disclose a weighing indicator set into the handle of a net and both devices described work in a similar manner. The fish is landed in the net and the hook removed from the fish's lip. The handle of the net is then held up vertically and the fish falls to the bottom of the net. The weight is then read from the display in the handle. The net may then be lowered back into the water and the fish released or kept in the net under water.
The problems with the two inventions above, are firstly when the net is held up to be weighed, the fish may get tangled up in the net when struggling to free itself. Elevation of the net handle causes an automatic wrap around effect on the fish with likely damage to the fins, gills and scales. Secondly, holding the net up vertically is cumbersome especially if the fish is large and may cause an injury to the fisherman. This may be a serious problem on a boat as the fisherman will have to haul the net and fish inboard thereby increasing the time the fish is out of water. Alternatively if he or she is next to the gunwale the risk of falling especially in a swell is significant. Finally the reading from an analogue display is inaccurate and difficult to read.